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At least 19 recordsLinked to original sources
PubMed1977

Bluetongue in cattle: effects of vector-transmitted bluetongue virus on calves previously infected in utero.

Three of 7 principal calves, after a challenge of immunity exposure by bites of bluetongue (BT) virus-infected Culicoides variipennis, became latently infected with BT virus. These calves were born to heifers infected with the homologous virus by bites of C variipennis at 60 or 120 days' gestation. Latent BT virus infection was detected by isolation of BT virus from washed erythrocyte samples obtained from the calves at 57, 100 to 102, 200 to 202, 300 to 302, and 400 to 402 days after challenge of immunity and from 1 of the calves over 5 years after challenge of immunity. The 3 latently infected calves were healthy; 2 were immunologically competent and 1 was immunologically incompetent to develop detectable BT virus antibodies in their blood. Bluetongue virus infection was detected (by viral isolation) in 2 other principal calves during the challenge of immunity, but they were not considered latently infected. The latter 2 calves were immunologically incompetent to develop detectable BT virus antibodies.

Animals↗
PubMed1977

Bluetongue in cattle: repeated exposure of two immunologically tolerant calves to bluetongue virus by vector bites.

A heifer and steer that were immunologically tolerant to bluetongue (BT) virus became immunologically competent after repeated exposures by bites of BT virus-infected Culicoides variipennis. Immunologic tolerance ended in the heifer at 25 months of age, after the 2nd exposure to the virus, and in the steer at 22 months, after the 4th exposure. High hemic concentrations of BT virus were detected in both animals after they became immunologically competent, but neither developed an overt BT clinical response. The steer died suddenly and extensive pathologic changes were observed at necropsy.

Animals↗
PubMed1975

Epizootiology of bluetongue: the situation in the United States of America.

Bluetongue was first reported in the United States in 1948 in sheep in Texas. The virus has now been isolated from sheep in 19 States. When the disease first occurs in a flock, the morbidity may reach 50 to 75% and mortality 20 to 50%. In subsequent years, the morbidity may be only 1 to 2% with very few deaths. Difference in breed susceptibility has not been observed. Natural bluetongue infection has not been observed in Angora or dairy goats. Bluetongue virus was first isolated from cattle, in Oregon, in 1959. The virus has now been isolated from cattle in 13 States. In cattle, the disease is usually inapparent but can cause mild to severe clinical disease and neonatal losses. Natural clinical bluetongue has also been reported in bighorn sheep, exotic ruminants in a zoo, mule deer, and white-tailed deer. Serological evidence of exposure to the virus has also been found in other species of ruminants in the wild. Inoculation of virulent bluetongue virus, vaccine virus, or natural disease can cause congenital deformities and neonatal losses in calves, lambs, and white-tailed deer fawns. Culicoides is considered the important insect vector of bluetongue. The virus has also been isolated from sheep keds and cattle lice. U.S. field strains of the virus fit into four serologic groups. No cross reactions were found between bluetongue and epizootic haemorrhagic disease of deer viruses. Cattle are considered significant virus reservoirs. It is necessary to use washed erythrocytes, rather than whole blood, and to inoculate susceptible sheep, rather than embryonated chicken eggs, to detect longer-term viraemia in cattle.

Animals↗
PubMed1978

Serological evidence of the occurrence of bluetongue in Iraq.

Precipitating antibodies against bluetongue were detected in sheep and goat serum samples collected from animals slaughtered in Baghdad abattoir. Out of 294 sheep serum samples and 110 goat serum samples examined, 28 and 18 samples respectively showed precipitating activity. In addition, examination of sheep serum samples collected from localities where clinical cases similar to bluetongue were previously reported revealed the presence of bluetongue precipitating antibodies in 101 sera out of 198 samples examined. This is the first report confirming the occurrence of bluetongue in Iraq.

Animals↗
PubMed1977

Sheep erythrocyte and bluetongue virus antibody responses of spleen cell cultures from mice.

The optimum conditions for the culture of cells from dissociated spleens were determined. Routinely, 10(7) cells were seeded per ml of RPMI 1640 medium supplemented with 20% pre-tested foetal calf serum. For the assay of the immune response, cultures were supplemented with 30 muMolar mercaptoethanol. The immune responses to sheep erythrocyte and bluetongue virus antigens were determined by the haemolytic plaque-forming cell assays described by Oellermann (1974) and Oellermann, Carter & Marx (1976a). The optimum sheep erythrocyte antigen concentration was 2 X 10(6) erythrocytes per 10(7) spleen cells and maximum IgM plaque-forming cells were detected after 4 days in culture. Successful stimulation of the immune response to bluetongue virus was achieved in spleen cell cultures from mice previously primed with bluetongue virus. The optimum antigen concentration was 30-40 ng bluetongue virus per 10(7) spleen cells and the maximum plaque-forming cell response was observed after 4 days in culture.

Animals↗
PubMed1975

The epizootiology of bluetongue: the African situation.

Bluetongue virus is transmitted biologically by various species of Culicoides, notably C. pallidipennis and C. variipennis. Factors such as rainfall, temperature and relative altitude, which influence the breeding of the insect vectors also govern the incidence and distribution of the disease. The host range of bluetongue virus includes sheep, cattle, goats and various antelopes. Many other, as yet unidentified hosts could perhaps harbour the virus and influence the epizootiology of the disease. The close relationship between C. pallidipennis and cattle is indicated and the efficient mechanism for virus maintenance which this relationship constitutes is emphasised. It is further postulated that sheep are not essential for the continued survival of bluetongue virus, but merely function as accidental or indicator hosts.

Africa, Southern↗
PubMed1976

Study on the pathogenesis of bluetongue: replication of the virus in the organs of infected sheep.

The pathogenesis of bluetongue infection was studied by the titration of the virus in tissue samples taken from sheep inoculated subcutaneously in the auricula of the ear with 76 TC ID50 of the plaque-purified type 10 bluetongue virus. Tissue samples were taken from individual animals killed at daily intervals over a period of 11 days. The mean incubation time was 6.9 days and the first clinical sign was pyrexia. On the 4th day, bluetongue virus was demonstrated in the lymph nodes of the cephalic area, tonsils and spleen; viraemia became demonstrable on the 6th day post-inoculation and typical macroscopic lesions due to the virus were first observed on the 8th day. It was concluded that, post-infection, the virus entered the regional lymph nodes. From there it was disseminated via the lymph and/or the blood stream to the lymphoid tissues in other parts of the body where further replication occurred. From these primary sites the virus was carried via the blood stream and infected the majority of tissues. Humoral antibody, as detected by immunofluorescence, did not appear to have a direct influence on the concentration of virus in solid tissues. Persistence of the virus in infected sheep was not demonstrated when tissues were taken 6, 8 and 16 weeks after infection.

Animals↗
PubMed1975

The control of bluetongue in an enzootic situation.

On account of the wide host range of bluetongue virus and its biological transmission by insects, control of the disease in an enzootic situation is based primarily on the active immunisation of susceptible animals as well as on the prevention of contact between the insect vectors and the susceptible hosts. In spite of their unquestionable value, the egg attenuated vaccines which are currently employed for prophylactic immunisation, have certain shortcomings. The existence of 16 known serotypes of bluetongue virus makes it difficult to achieve a very wide spectrum of immunity in sheep vaccinated once or twice only. The problems which are experienced with the immunisation of lambs born in spring are indicated. The present vaccine can also present problems when used in breeding animals. Furthermore, the costs involved in the annual vaccination of large numbers of animals are considerable. The need for a vaccine for cattle is indicated. Work is also being conducted at present on the development of an inactivated vaccine for use in sheep. The use of novel virological techniques may aid in the future development of absolutely safe and highly efficient vaccines against bluetongue.

Animals↗
PubMed1975

Antigenic and morphologic comparisons of Ibaraki and bluetongue viruses.

Bluetongue disease virus, type 10, and Ibaraki disease virus, which causes a bluetongue-like disease of cattle, were compared to determine whether they are the same or different viruses. They were similar in morphology, but neutralization tests, complement-fixation tests, and ferritin tagging indicated that they have antigenic differences. Therefore, they should be considered as different viruses. Two other viruses of this group, African horsesickness and equine encephalosis, were included to show that Ibaraki and bluetongue had developmental morphological features that could be used to differentiate them from the two equine viruses.

Animals↗
PubMed1978

The use of cattle to protect sheep from bluetongue infection.

Studies on the host preferences of Culicoides imicola, the vector of bluetongue virus in South Africa, are reviewed. There is agreement that this species prefers to feed on cattle but will also feed on other bovidae and sheep. Over a seven year period cattle kept near sheep on a Natal farm appear to have appreciably reduced the incidence of bluetongue in the sheep. In addition to immunization this "decoy" approach is therefore recommended to assist in the protection of stock from insect borne diseases such as bluetongue and possibly African horsesickness and Rift Valley fever.

Animals↗
PubMed1978

The 1977 outbreak of bluetongue in Cyprus.

Bluetongue outbreaks, ranging from isolated cases to widespread infections, have occurred in Cyprus in about half of the years since 1924. Serious outbreaks occurred in 1924, 1939, 1943, 1946, 1951, and 1965. Most cases occurred in September, October, November and December. The last outbreak prior to 1977 was in 1969. Virus types isolated in the past were types 3 and 4. In 1977 the outbreak was serious, affecting 13.1 per cent of 27,837 in-contact sheep; these were scattered in 303 flocks of 65 villages throughout the Government-controlled area. The virus type isolated was type 4. Culicoides were involved in bluetongue transmission in the island.

Animals↗
PubMed1975

Bluetongue: the disease in cattle.

Most researchers in South Africa found that although BT virus could be isolated from apparently healthy cattle and from inoculated cattle the virus did not produce overt clinical disease in cattle. However, when epizootics were reported outside Africa, clinical signs were observed in cattle in Israel, Palestine, Syria, Portugal, and Spain. Most natural BT infections in cattle in the United States do not result in overt clinical signs. However, in certain infected herds, approximately 5% of the cattle show from mild to severe disease. Except for severe cases, spontaneous recovery is usual. The clinical diagnosis of BT in cattle is difficult and requires laboratory assistance. Culicoides variipennis can serve as a vector of BT virus from cattle to cattle, cattle to sheep, sheep to cattle, and sheep to sheep. In utero transmission occurs in cattle and can result in abortion, hydraencephaly, congenital deformity, and birth of viraemic calves which may or may not develop BT antibody. Calves inoculated in utero or those born to infected dams may have a persistent viraemia with or without BT antibody. tone such animal has been held in insect-secure quarters and has continued to harbour virus for 3 years. Bluetongue virus was isolated from the semen of experimentally infected bulls. Calves inoculated with BT virus and also given an immuno-suppressant developed marked clinical disease in 8 to 12 days. Bluetongue virus is very closely associated with the erythrocytes of infected cattle, sheep, and goats. Cattle are considered important and relatively long-term virus reservoirs. In attempts to determine the maximum period of viraemia in cattle it is necessary to inoculate washed erythrocytes, rather than whole blood, and to use susceptible sheep as the assay system rather than embryonated chicken eggs.

Abortion, Veterinary↗
PubMed1975

Ibaraki disease and its relationship to bluetongue.

Ibaraki disease, an epizootic disease of cattle in Japan resembling bluetongue, is characterized by fever and lesions affecting the mucous membranes, the skin, the musculature and vascular system. Degeneration of striated muscular tissue is observed in the oesophagus, larynx, pharynx, tongue and the skeletal muscles. Oedema and haemorrhage are marked in the mouth, lips, abomasum, around the coronets, etc., and are occasionally followed by degeneration of the epithelium leading to erosions or ulcerations. Severe lesions affecting the oesophageal and laryngopharyngeal musculature cause difficulty in swallowing which in turn produces dehydration and emaciation, and occasionally the aspiration pneumonia, which constitute the major causes of death of affected animals. These clinical and pathological findings indicate the similarity of the disease to bluetongue in sheep and cattle. Ibaraki disease was first recognised in Japan in 1959 and 1960. Seasonally its occurrence is limited to late summer and autumn, and geographically to the central and western parts of Japan, roughly south of 37 degrees north latitude. It is absent from the higher altitudes. The seasonal and geographical incidence suggests the possibility of an arthropod vector; but direct evidence for such a vector is still lacking. Serological data suggest the presence of Ibaraki virus on Bali Island in Indonesia and in Taiwan. The disease can be transmitted serially in calves by the intravenous inoculation of blood obtained at the height of a febrile reaction. Ibaraki virus can be isolated in bovine cell cultures from both natural and experimentally produced cases of the disease. The virus multiplies and induces cytopathic effects in primary cultures of bovine, sheep and hamster lung origin, and L cells; but it does not grow in primary cultures of horse and swine kidney nor in HeLa cell cultures. The virus is readily passaged serially in 4 to 5-day-old eggs by yolk-sac inoculation and incubation at 33.5 degrees C. It multiplies in the brains of mice of any age after incracerebral inoculation but younger mice give a better viral growth and develop encephalitis. No evidence has been obtained that rabbits and guinea pigs are susceptible to Ibaraki virus...

Animals↗
PubMed1979

Preliminary observations on transplacental infection of bluetongue virus in sheep-a possible overwintering mechanism.

Sheep infected mid-gestation with bluetongue virus type 4 and type 16 produced clinically normal lambs that were viraemic at birth. Viraemia persisted for two months in some lambs even though they received colostrum. It is suggested that transplacental infection of bluetongue virus in sheep may be an overwintering mechanism for the virus in some areas of the world.

Animals↗
PubMed1978

Possible windborne spread of bluetongue to Portugal, June-July 1956.

The possible sources for the epidemic of bluetongue in Portugal at the beginning of July 1956 were examined. Introduction through authorized importation of domestic or wild ruminants was not feasible, since no cattle, sheep or goats were imported and the wild ruminants were confined to Lisbon Zoo, which was too far from the initial outbreaks. Weather maps were examined to see if the wind could have carried infected Culicoides midges from North Africa. On 21 June 1956 infected midges in Morocco could have been taken offshore by southeast winds and then carried by south winds unusual at that time of year to the south coast of Portugal. The 200-300 km sea crossing would have taken some 10 h and been by day when air temperatures near the sea surface were about 18-20 C. Bluetongue had not been reported at that time in Moroccco, and the possibility of the presence of the virus in moroccan animals without clinical signs is discussed.

Air Movements↗
PubMed1976

Serial cyclic transmission of bluetongue virus in sheep and Culicoides variipennis.

Bluetongue virus (strain 62-45S) was transmitted from sheep to sheep throughout a year by vector bites. A colonized population (SONORA strain, 000 line) of the biological vector Culicoides variipennis (Coquilllett) was used. Fifteen serial cyclic transmissions covered a period of 13 months from October through November of the following year. The mean infection rate of the biting gnats was 37 percent. The clinical response to bluetongue virus was significantly more severe in sheep infected by vector bites than in those inoculated with the virus at the same sheep-serial passage level. A second corroborative serial transmission was conducted for 7 months from June through December. The mean infection rate of the vector was 27%.

Animals↗
PubMed2026

Longitudinal whole-genome analysis of bluetongue virus identifies conserved serotype-specific genomes and distinct genomic constellations within a Colorado sheep flock (2021-2023).

Bluetongue virus (BTV) is a segmented double-stranded RNA virus of ruminants transmitted by Culicoides spp. biting midges. Although the genome consists of ten segments, classification into serotypes is primarily based on genome segment 2. However, reassortment among genomic segments is a major driver of BTV evolution and diversity. This study used longitudinal whole-genome sequencing to characterize BTV genomes collected from 2021 to 2023 within a single sheep flock in Colorado, where multiple serotypes co-circulate. Whole-genome sequences were generated from fourteen blood samples representing four serotypes: BTV-6, -11, -13, and -17. Longitudinal sampling identified multiple BTV serotypes within individual sheep across consecutive years. Tanglegram analysis comparing segment phylogenies to the segment 2 tree demonstrated incongruent topologies across all genomic segments, suggestive of reassortment or the circulation of distinct genomic constellations. Nucleotide-level comparisons revealed high sequence homology among same-serotype samples from the same year, while the greatest genetic divergence was observed among BTV-17 genomes collected in different years. Additionally, all BTV-13 genomes contained a previously undescribed nonsynonymous substitution in segment 10 predicted to extend the encoded protein by three amino acids. Together, these findings demonstrate that highly conserved BTV genomes and distinct genomic constellations can be detected at the flock level across multiple years. This longitudinal whole-genome approach reveals the genetic complexity of endemic BTV populations, including novel variants and genomic patterns consistent with reassortment that are lost with conventional serotyped-based approaches, highlighting the need to integrate whole-genome characterization into endemic BTV monitoring programs.

Animals↗